Reliability of neural entrainment in the human auditory system.

Auditory stimuli are often rhythmic in nature. Brain activity synchronizes with auditory rhythms via neural entrainment, and entrainment seems to be beneficial for auditory perception. However, it is not clear to what extent neural entrainment in the auditory system is reliable over time - a necessary prerequisite for targeted intervention. The current study aimed to establish the reliability of neural entrainment over time and to predict individual differences in auditory perception from associated neural activity. Across two different sessions, human listeners (21 females, 17 males) detected silent gaps presented at different phase locations of a 2-Hz frequency modulated (FM) noise while EEG activity was recorded. As expected, neural activity was entrained by the 2-Hz FM noise. Moreover, gap detection was sinusoidally modulated by the phase of the 2-Hz FM into which the gap fell. Critically, both the strength of neural entrainment as well as the modulation of performance by the stimulus rhythm were highly reliable over sessions. Moreover, gap detection was predictable from pre-gap neural 2-Hz phase and alpha amplitude. Our results demonstrate that neural entrainment in the auditory system and the resulting behavioral modulation are reliable over time, and that both entrained delta and non-entrained alpha oscillatory activity contribute to near-threshold stimulus perception. The latter suggests that improving auditory perception might require simultaneously targeting entrained brain rhythms as well as the alpha rhythm.Significance StatementNeural activity synchronizes to the rhythms in sounds via neural entrainment, which seems to be important for successful auditory perception. A natural hypothesis is that improving neural entrainment, e.g., via brain stimulation, should benefit perception. However, the extent to which neural entrainment is reliable over time - a necessary prerequisite for targeted intervention - has not been established. Using electroencephalogram recordings, we demonstrate that both neural entrainment to FM-sounds and stimulus-induced behavioral modulation are reliable over time. Moreover, moment-by-moment fluctuations in perception are best predicted by entrained delta phase and non-entrained alpha amplitude. This work suggests that improving auditory perception might require simultaneously targeting entrained brain rhythms as well as the alpha rhythm.